Effect of electrolyte composition on the microstructure and bio-corrosion behavior of micro-arc oxidized coatings on biomedical Ti6Al4V alloy

In view of the low bioactivity and the inability to form bone fusion with surrounding bones in vivo, bioactive ceramic coatings were prepared on the bio-inert Ti6Al4V (TC4) alloys by micro-arc oxidation (MAO) technology in two different electrolytes. The effects of electrolyte composition and applied positive voltage on the microstructure and corrosion resistance of the MAO coating were studied. The surface morphology, composition, and microstructure of the MAO coatings were systematically characterized. The corrosion behaviors of the MAO coatings were studied by electrochemical corrosion test and simulated body fluid (SBF) immersion test in vitro. After soaking in SBF solution, CaP apatites formed on the surface of the MAO coatings. Results showed that the MAO coatings obtained from the silicate electrolyte grew rapidly and corroded faster in SBF solution, while MAO coatings obtained from the calcium phosphate electrolyte had excellent surface and corrosion resistance properties. The formation and corrosion mechanisms of the MAO coatings obtained from the two different electrolytes were discussed.